Enhanced stability of carbon-based perovskite solar cells by using n-butylamine to assemble 2D capping layer

Hybrid organic-inorganic perovskite solar cells (PSCs) lack long-term stability, and this negatively impacts the widespread application of PSCs. Two-dimensional (2D) perovskite regarded as an emerging of photovoltaic materials, exhibits excellent environmental stability than three-dimensional (3D) perovskite due to existence of the long-chain organic ligands. Herein, aiming to increase the stability of the device, we introduce a thin 2D perovskite capping layer by the reaction of n-butylamine (BA) with 3D perovskite film to form 2D capping layer. Eventually, this process enhances crystallinity of perovskite active layer and photophysical properties of PSCs. The resulting PSCs based on carbon-counter-electrode yields a power conversion efficiency (PCE) from 8.75% to 10.39%. Under the protection of carbon electrode and 2D capping layer, the stability of PSCs has been greatly improved. The unencapsulated device with 2D/3D active layer remained 93% of the original value of PCE after 55 days in air with humidity of about 50% at room temperature. This work can provide an easy and inexpensive way to improve the stability and efficiency of PSCs.